1. Field of the Invention
The present invention relates to a method and fluid additive for use in treating subterranean formations containing clays and particularly for use in stimulation fluids such as fracturing fluids.
2. Prior Art
Production of oil and gas often is troubled by the presence of clays and other fines capable of migrating in the formation. Normally, the clays and fines are stable and cause no obstruction to the flow of hydrocarbons through a subterranean formation. However, when the clays or fines are disturbed, such as by contact with an aqueous fluid that is foreign to the formation, the clays can swell or the fines can migrate through the capillary flow channels in the formation resulting in a loss of a formation permeability.
There have been numerous attempts to control the ill effects of introduced aqueous fluids upon clays and other fines contained in subterranean formations. One idea has been to convert the clay from a swelling form by cation exchange to a less swelling form. This method of control is attempted through the addition of various well known salts to the aqueous fluids utilized in the treatment of subterranean formations. Salts such as potassium chloride, calcium chloride, ammonium chloride and the like typically are dissolved in the aqueous fluid utilized to effect the formation treatment. The solubilized salts effect ion exchange with the charged particles comprising the clays. While these salts often are effective at protecting a formation, they can be very detrimental to the performance of other constituents of the treatment fluid. As a result of the difficulty of dissolving the various salts in a viscosified fluid, through an inability to effect adequate mixing for the large volumes of salts required in the commercially available mixing equipment utilized in oil field services, the salts typically are admixed with the aqueous fluid before admixture of any viscosifying or gelling agents to the aqueous fluid. The salts, however, may have a detrimental effect upon the viscosity yield by the gelling agent upon hydration in the aqueous fluid.
It would be desirable to provide a method and additive by which a subterranean formation could be protected from the effects of foreign aqueous fluids and stimulation fluids could be prepared simply and without detrimental effects to fluid constituents.